Telephone answering is a telephone on-hook capability that provides a calling party who encounters a no-answer situation with the possibility of recording or leaving a message for the called party in response to a pre-recorded voice prompt. Such services are presently provided either as a central office or network function or through the use of customer premise equipment (CPE) customarily known as answering machines. When such an answering service is provided through the central office the called party may ascertain that a call was received by picking up the receiver to create an off-hook condition whereupon the central office provides an interrupted or stutter dial tone to indicate that a call was received and that any message may be retrieved. In the case of a CPE answering machine an indication that a call occurred is usually provided through an indicator light on the telephone answering machine. In the case of private branch exchange (PBX) systems an indicator light is commonly provided on the telephone instrument to serve as a message light. Examples of patents illustrating various forms of such notification include the following:
Applebaum U.S. Pat. No. 3,320,368 describes a hotel-type telephone set having a signal lamp. A battery powered ringing signal detector is provided to energize the signal flasher lamp and activate it to indicate that a message is waiting.
Myslinski et al U.S. Pat. No. 4,582,959 describes a PBX telephone answering message storage system which either permits storage of a message or stores a call back message on demand from a caller. In either case the system actuates an automatic message waiting lamp at the intended station in response to the storage of the message.
Schmitt U.S. Pat. No. 4,506,115 describes a message waiting lamp system wherein each hand set is provided with a message waiting lamp and a transmitter for actuating that lamp in response to an out of band signal.
Boeckmann U.S. Pat. No. 4,648,109 describes another PBX extension telephone message waiting indication in the form of an LED controlled from the PABX.
Yuan U.S. Pat. No. 4,280,021 discloses a signal waiting lamp activator for a PABX system.
Duff et al U.S. Pat. No. 3,742,792 describes a message waiting lamp and controller for use with key telephone systems.
In addition to the foregoing ROMAR Ltd. of Colorado Springs, Colo., has advertised a voice message waiting indicator that is a customer premise based product that automatically detects the presence of stutter dial tone on a central office, Centrex, or PBX line and activates a message-waiting light. The device is designed to be connected between the telephone set and a modular RJ11 jack. The device is said to begin an automatic detection process after an unanswered incoming call, after any off-hook resulting from an incoming or outgoing call, or periodically to detect system messages left when no call was placed to the user's telephone.
ALLTEL Supply of Norcross, Ga., has advertised a so-called Message Monitor which is said to allow users of a network-based voice mail service to call screen messages as they are being left within the network voice mailbox. The device appears to be relatively complex to program and entails the disadvantage of requiring an internal voice mail prompt (contained within the unit itself), before allowing the caller to leave a message within the network-based voice mailbox. In other words, two separate sets of prompts must be handled by the caller to arrive at the greeting in a subscriber's voice mailbox. There is also a time delay as a result of this requirement, approximately forty seconds, and the disadvantage of allowing the caller to hear a number of switch hook relays before the call arrives at the voice mailbox. In addition, this device includes circuitry to allow unanswered incoming calls to be automatically forwarded to a voice mail system (or to any other telephone number) using the standard central office 3-way calling feature. As the incoming call is forwarded, a speaker is activated enabling the user to monitor the message being left by the caller as is common in CPE telephone answering machines. The device is said to be usable with any single-party line equipped with tone dialing, 3-way calling and a touch tone telephone. The device is said to be fully programmable using a telephone touch tone dial at the point of sale, at the customer location, or from a remote location. The device includes a power supply which plugs into a standard AC outlet.